June 21 is National Selfie Day, so fire up your smartphone, show off your healthy smile and snap a selfie. Post it to your favorite social media outlet with the hashtag #NationalSelfieDay.

We upload 350 million photos to Facebook, 95 million photos on Instagram and 3 billion snaps on Snapchat each day, according to a new book, Selfies, Why We Love (and Hate) Them, by Katrin Tiidenberg of Denmark’s Aarhus University. But honestly, how interesting would all those posts be without selfies? Selfies are a good way to show off our healthy smiles and express ourselves to the world – and they can actually reveal a lot about us in the process, for better or worse!

Selfies just started gaining popularity with the rise of smartphones and social media, but they aren’t really new. In fact, they date back to the 16th century. The first selfie was created in 1524 when 21-year-old artist Parmigianino painted his own reflection in oil on wood. He titled it “Self-Portrait in a Convex Mirror,” of course!

The first photographic selfie was taken by Robert Cornelius in 1839, and he had to work hard to produce the daguerreotype of himself! Cornelius had to set up the camera on a stand, remove the lens cap, run into the frame, sit for five minutes, then sprint back and replace the cap. Selfies have definitely come a long way!

Compare Cornelius’ feat to Kim Kardashian’s: In May 2015, she published a book called Selfish, which is 448 pages long and comprised entirely of her favorite selfies. It sounds silly, but Selfish quickly became a New York Times bestseller! It just goes to show the fascination we have with selfies in our social media-obsessed society.

Here are more fun facts about selfies:

They made the Oxford: The word “selfie” was named Oxford Dictionaries’ Word of the Year in 2013 and is now joined in the Oxford Dictionary by “selfie stick.”

They are a window to your soul: A report from Computers in Human Behavior indicates that your selfie post can reveal a lot. For example, people who look directly into the camera are more agreeable, while those who pose with duck lips might be mentally unstable.

Selfie addiction is real: If more than 50% of the pics you take are selfies, you might have “selfitis.” Psychologists say selfie addiction is a real mental health issue that can result in suicide.

Some cities “selfie” more than others: Time magazine created a database of more than 400,000 digital self-portraits with the caption “#selfie” and then mapped out the photos’ geographic coordinates. Time ranked 459 cities based on the number of selfies they took. Makati City in the Philippines was found to be the “Selfie Capital of the World,” followed closely by Manhattan and Miami.

Millennials love their selfies: The average age of selfie-takers is 23.6, and the average millennial is expected to take 25,700 selfies during the course of his/her lifetime. That’s almost one a day, every day, for their entire lives.

Everyone uses filters: According to a survey, 68% of selfie-takers admitted to editing their photos before sharing them online – up from 48% of people who admitted to doing so in 2014 – suggesting that societal pressure to appear perfect has only increased.But selfies need not be perfect – just have fun expressing yourself! A healthy smile always makes for the best selfies. At SleepRight, we want to help ensure you have healthy smiles and stunning selfies. If the nighttime grind is putting your gorgeous grin at risk, wear a custom-fit, no-boil dental guard to help protect your pearly whites while you sleep. Visit www.sleepright.com to find out more.